Presently running 1P/Mac 3.5.15 and 1P/Mac 4b45 (in parallel) on my MacBookPro8,1 and the current version of 1P/iOS on my iPhone 4S.
Syncing via Dropbox only.
A few days ago I added a credit card on my iPhone and was disturbed to not find it on my Mac the following day.
Since then, the All Items count on my iPhone has been steadily diverging from the count on both 1P/Mac apps and changes on either platform are not syncing to the other.
The sync animation in 1P/iOS looks normal, and to all appearances Dropbox is functioning properly on my Mac as well.
I can solve my immediate problem by manually transfer the newly-added stuff from my iPhone to my Mac and then reset 1Password on my iPhone, but I thought that, before doing so, I should post something here and see if I could do some troubleshooting that might be helpful to others. :-)